1. Technical Field
The present invention relates to a printed circuit board using bumps and a manufacturing method thereof, and more particularly, to a printed circuit board formed by collectively stacking multilayer and a manufacturing method thereof.
2. Description of the Related Art
A conventional multilayer printed circuit board has been prepared by forming inner layer circuits on the surface of a core board, such as copper clad laminate (CCL), etc., through the application of an additive method or a subtractive method, and by forming outer layer circuits through stacking of insulation layers and metal layers in order, by the same method as for forming the inner layer circuit.
With developments in electronic components, there is a demand for technology which can improve the performance of HDI (high density interconnection) boards, to which the concepts of interlayer electrical connection and micro circuit wiring have been applied for higher density printed circuit boards. That is, to improve the performance of HDI boards, a technology is required which provides interlayer electrical connection and an adequate degree of freedom.
The method of manufacturing a multilayer printed circuit board according to conventional technologies includes first perforating through holes in a core board (e.g. a CCL, etc.) by mechanical drilling, etc., forming plating layers by chemical copper plating and/or copper electroplating, etc., on the surfaces of the core board and on the inner perimeters of the through holes, and then forming inner layer circuits on the surfaces of the core board by applying an additive or a subtractive process, etc., and inspecting the circuits.
Next, a build-up process is performed by procedures of surface treatment and stacking RCC (resin coated copper), etc., and through holes are formed for interlayer electrical connection between circuits by laser drilling, etc. and the surface of the through holes is plated, after which outer layer circuits are formed on the surface of the stacked board and the circuits are inspected. To add more layers of circuits, the process is repeated of surface treatment and stacking RCC, etc., forming through holes, plating the surfaces of the through holes, and afterwards forming outer layer circuits. Such a build-up process is repeated to form a desired number of circuit layers.
However, the conventional manufacturing process for multilayer printed circuit boards is unable to comply to requests for low costs according to lowering prices in the applied products (e.g. cell phones, etc.) and requests for reduced lead times for increased productivity, and thus there is a demand for a new manufacturing process that can resolve such problems.
In order to simplify the complicated process of related art and to manufacture a multilayer printed circuit quickly and inexpensively by a collective stacking procedure, the so-called “B2IT (buried bump interconnection technology)” has been commercialized, which allows a simple and convenient stacking process by printing paste on a copper foil 3 to form bumps 2′ and stacking an insulation material 1 thereon to prefabricate a paste bump board, as illustrated in FIG. 1.
Related art to the paste bump board includes an invention which uses a paste bump board having bumps made of conductive paste formed on a copper foil to allow simple and easy interconnection between the terminals of high-density electronic components. This, however, implements all-layer IVH's with only the paste bump board so that it has a weak structure and there is also a limit to reducing thickness of the board to be used as an inner layer core board due to limitation of the processing of through holes. Also, there is a difficulty of guaranteeing an interlayer electrical connection and a degree of freedom to improve the performance of HDI or BGA boards and provide excellent heat-releasing effect.